Florent Morel

A Comparative Study of Predictive Current Control Schemes for a Permanent-Magnet Synchronous Machine Drive

This paper presents a comparative study of three predictive current control schemes for permanent-magnet synchronous machine (PMSM) drives. The first control scheme predicts the future evolution of the currents for each possible configuration of the inverter legs. Then, the switching state which minimizes a given cost function is selected and applied during the next sampling time. The second control scheme uses a modulator to apply two configurations of the inverter legs during a computation period. Among these configurations, one leads to null voltages. The duration of the other configuration is calculated in order to minimize the distance between the obtained state vector and the desired one. The third control scheme uses a model of the PMSM in order to predict the stator voltages which allows us to reach the desired currents after one modulation period. An algebraic method is presented to compute the duty cycle of each leg of the inverter in a direct manner. These control schemes are detailed and tested using the same switching frequency on the same test bench (1.6-kW PMSM drive). A simulation study is performed in order to compare sensitivity to parameters of each control scheme. Experiments confirm the simulation results.

Implementation of Hybrid Control for Motor Drives

This paper presents the implementation of a hybrid-control strategy applied to a permanent-magnet synchronous-motor (PMSM) drive. Hybrid control is a general approach for control of a switching-based hybrid system (HS). This class of HS includes a continuous process controlled by a discrete controller with a finite number of states. In the case of ac motor drives, in contrast to conventional vector control like proportional-integral control or predictive control, where the inverter is not taken into account by the controller, hybrid control integrates the inverter model and considers the state of the inverter as a control variable. It allows to obtain faster torque dynamics than vector-control algorithms. The hybrid control algorithm requires both computing velocity for real-time implementation and code flexibility for management of low-performance functions and analog-digital interfaces. Codesign appears as a promising methodology for partitioning hybrid-control algorithm between software (flexible) and hardware (velocity) while taking care of overall time constrains. In this paper, the implementation of hybrid-control algorithm for a PMSM drive is performed through a codesign approach on an Excalibur board, embedding a CPU-core (Nios-2 by Altera) inside an APEX20KE200EFC484-2X field-programmable gate array. The partitioning of software and hardware parts is explained. Experimental results show the effectiveness of the implementation. Performances, advantages, and limitations are discussed.

Permanent Magnet Synchronous Machine Hybrid Torque Control

This paper presents a control scheme suitable for systems composed of a continuous process modulated in energy by a power converter with a finite number of topologies. To track the continuous reference values, a topology of the power converter is determined from a criterion based on a process state variable model and taking into account the possible topologies of the power converter. The proposed hybrid control scheme is applied to an electrical motor drive composed of an inverter coupled to a permanent magnet synchronous machine. An evolution which insures a fixed modulation frequency is also proposed. Experimental results validate the feasibility and effectiveness of the proposed schemes.

Self-starting DC:DC boost converter for low-power and low-voltage microbial electric generators

This paper describes and evaluates an original boost converter able to harvest energy from low-power and low-voltage power sources. Design and sizing are made according to specifications issued from the stringent characteristics of microbial electric generators such as microbial fuel cells and microbial desalination cells. The harvested power is 10mW under input voltage Vin=0.3V (33mA input current). The design of the converter is adapted from a classical boost topology. It includes a self-oscillating circuit for autonomous operation, and a simple analog maximum power point regulation. Measurements of the conceived discrete realization enable evaluation of the circuit. Best global efficiency of 74% is achieved under realistic harvesting conditions.

A Digital-Controller Parameter-Tuning Approach, Application to a Switch-Mode Power Supply

Analogue control of monolithic DC/DC converters is technologically coming to a limit due to high switching frequency and a request for large regulation bandwidth. Digital control is now experimented for low-power low-voltage switch-mode power supply. Digital implementation of analogue solutions does not prove real performances. This paper compares a classical digital controller to a candidate alternative strategy. Sensitivity functions are used to compare controller performances. An off-line approach using fuzzy logic to quantify controller performances and a genetic algorithm to obtain an optimal controller is presented. A so-called RST algorithm optimized with this approach shows better performances.

A predictive control for a matrix converter-fed permanent magnet synchronous machine

Many research efforts have been dedicated to matrix converters for several years. As major technological issues are now solved, this structure will widespread in industrial applications, in particular with AC motors. Current control is a key issue for AC motor drives, so many control schemes have been proposed. Some of them proposed at first for inverters, were applied to matrix converters. Among algorithms used with inverters, predictive control shows very good performances. In this paper a new control scheme is proposed for a matrix converter- fed permanent magnet synchronous machine. Literature about matrix converter technology and control and about predictive control for inverter-fed AC machines is reviewed. The proposed predictive control principle, the model of the whole machine - converter and the cost-function are detailed. The method offers a trade-off between the quality of motor currents and input power factor. Finally experimental results are reported. The feasibility and the effectiveness of the proposed method is assessed.

Hybrid control of a three-cell converter associated to an inductive load

This paper presents a control scheme for a multilevel multi-cell converter. For this type of converters, load current and capacitor voltages must be jointly controlled. Moreover the real-time constraint is important. This constraint leads us to propose a control based on a simplified state-space model. The model allows predicting the state vector evolution for every converter configuration. The control algorithm directly determines the converter switching state which minimizes a simple cost function. A normalization of the state variables is proposed for the cost function calculation in order to ensure a trade-off between the tracking of the load current and the tracking of the capacitor voltages. The proposed control scheme is detailed and compared with a classical control scheme with simulations. Finally, experimental results are presented to show the effectiveness of the proposed method.

Thermal Stability of Silicon Carbide Power JFETs

Silicon carbide (SiC) JFETs are attractive devices, but they might suffer from thermal instability. An analysis shows that two mechanisms could lead to their failure: the loss of gate control, which can easily be avoided, and a thermal runaway caused by the conduction losses. Destructive experimental tests performed on a dedicated system show that the latter mechanism is more severe than initially expected. A low thermal resistance and gate driver equipped with protections systems are thus required to ensure safe operation of the SiC JFETs.

A 140 mV Self-Starting 10 mW DC/DC Converter for Powering Low-Power Electronic Devices from Low-Voltage Microbial Fuel Cells

This paper presents an original self-starting DC/DC converter for low-power and low-voltage applications such as energy harvesting from microbial fuel cells to supply low-power electronic devices. Design is performed according to specifications issued from the stringent characteristics of microbial fuel cells. The harvested power reaches 10 mW under 0.3 V input voltage for the ten 1.3-liter experimental microbial fuel cells connected in parallel. The converter is adapted from a boost topology. It includes a self-oscillating sub-circuit for autonomous operation and a simple analog input-voltage control to harvest maximum energy from the source. The paper presents experimental results from a discrete and low-cost prototype. A global efficiency of more than 73% is achieved for 0.3 V input-voltage and under realistic harvesting conditions for the MFCs and the converter prototype.

Measurements and Simulation of Common Mode Conducted Noise Emissions in Adjustable-Speed AC Drive Systems

In order to efficiently reduce EMI emissions, especially common mode (CM) conducted noise emissions that are the most disturbing in any adjustable-speed drive systems, behaviour understanding and propagation path knowing of parasitic currents in the system are indispensable. In this paper, a simple CM disturbances modelling is proposed to estimate or calculate the CM noise currents. The modelling principle is based on specific experimental characterizations and on the modelling of the complete CM circuit considered as a chain of quadripolar matrices. Each part of the system is represented by a two-port network associated in cascade by using transfer matrix [T]. The comparison between calculations and experiments in an adjustable-speed drive system confirms effectively the validity of the proposed approach. Parametric studies carried out herein using this valid model will show in which way CM currents could be reduced or eliminated in a considered existing system.